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National Drug Strategy Household Survey 2013 – Data Quality Statement

Identifying and definitional attributes

Metadata item type:Help on this termQuality Statement
Synonymous names:Help on this termData Quality Statement: 2013 National Drug Strategy Household Survey
METeOR identifier:Help on this term558897
Registration status:Help on this termAIHW Data Quality Statements, Endorsed 25/11/2014

Data quality

Quality statement summary:Help on this term
  • The National Drug Strategy Household Survey (NDSHS) provides three-yearly estimates of the proportion of the population aged 12 years and older using tobacco, alcohol and illicit drugs. The Survey also captures information about drug-related attitudes, perceptions and support for government policy.
  • It is known from past studies of alcohol and tobacco consumption that respondents tend to underestimate actual consumption levels.
  • Estimates of illicit drug use and related behaviours are also likely to be underestimates of actual practice.
  • Reported findings are based on self-reported data and are not empirically verified by blood tests or other screening measures.
  • The response rate for the 2013 survey was 49.1%. Given the nature of the topics in this survey, some non-response bias is expected, but this bias has not been measured.
  • Both sampling and non-sampling errors should be considered when interpreting results.
Institutional environment:Help on this term

The Australian Institute of Health and Welfare (AIHW) is a major national agency set up by the Australian Government under the Australian Institute of Health and Welfare Act 1987 to provide reliable, regular and relevant information and statistics on Australia's health and welfare. It is an independent statutory authority established in 1987, governed by a management Board, and accountable to the Australian Parliament through the Health and Ageing portfolio.

The AIHW aims to improve the health and wellbeing of Australians through better health and welfare information and statistics. It collects and reports information on a wide range of topics and issues, ranging from health and welfare expenditure, hospitals, disease and injury, and mental health, to ageing, homelessness, disability and child protection.

The Institute also plays a role in developing and maintaining national metadata standards. This work contributes to improving the quality and consistency of national health and welfare statistics. The Institute works closely with governments and non-government organisations to achieve greater adherence to these standards in administrative data collections to promote national consistency and comparability of data and reporting.

One of the main functions of the AIHW is to work with the states and territories to improve the quality of administrative data and, where possible, to compile national datasets based on data from each jurisdiction, to analyse these datasets and disseminate information and statistics.

The Australian Institute of Health and Welfare Act 1987, in conjunction with compliance to the Privacy Act 1988, (Cth) ensures that the data collections managed by the AIHW are kept securely and under the strictest conditions with respect to privacy and confidentiality.

For further information see the AIHW website www.aihw.gov.au

The NDSHS has been analysed and managed by the AIHW since 1998 and 2001 (respectively).

Timeliness:Help on this term

The NDSHS is conducted approximately every three years over a three-four month period. 2013 data were collected between late-July and early December 2013.

A preliminary data set was received by the AIHW in late-January 2014 and initial data checks were completed in early February 2014.

Key findings from the 2013 NDSHS were released on 17 July 2014.

Accessibility:Help on this term

Results from the 2013 NDSHS are available on the AIHW website. Key findings can be found in the web compendium: Highlights from the 2013 survey and full published results can be found in the 2013 National Drug Strategy Household Survey report.

Users can request data not available online or in reports via the Communications, Media and Marketing Unit on (02) 6244 1032 or via email to info@aihw.gov.au. Requests that take longer than half an hour to compile are charged for on a cost-recovery basis.

A confidentialised unit record file is available for 3rd party analysis through the Australian Data Archive. Access to the master unit record file may be requested through the AIHW Ethics Committee.

 

Interpretability:Help on this term

Information to aid in interpretation of 2013 NDSHS results may be found in Chapter 1 of the 2013 NDSHS report titled ‘Introduction’.

In addition, the 2013 Technical Report, code book and other supporting documentation are available through the Australian Data Archive website or may be requested from AIHW.

Relevance:Help on this term

Scope and coverage
The NDSHS collects self-reported information on tobacco, alcohol and illicit drug use and attitudes from persons aged 12 years and over.

Excluded from sampling were non-private dwellings (hotels, motels, boarding houses, etc.) and institutional settings (hospitals, nursing homes, other clinical settings such as drug and alcohol rehabilitation centres, prisons, military establishments and university halls of residence). Homeless persons were also excluded as well as the territories of Jervis Bay, Christmas Island and Cocos Island.

The exclusion of people from non-private dwellings and institutional settings, and the difficulty in reaching marginalised people are likely to have affected estimates.

The 2013 NDSHS was designed to provide reliable estimates at the national level. The survey was not specifically designed to obtain reliable national estimates for Aboriginal and Torres Strait Islander people, as there was no target sample size for Indigenous Australians. In 2013, the sample size for Indigenous Australians was smaller than anticipated based on population estimates, and so estimates based on this population group should be interpreted with caution.


Reference period
The fieldwork was conducted from 31 July to 1 December 2013. Respondents to the survey were asked questions relating to their beliefs and experiences covering differing time periods, predominantly over the previous 12 months.


Geographic detail
In 2013, data were coded to the census collector’s district level. Data are generally published at the national level with a selection of data published at the State/Territory and Remoteness Area levels.


Statistical standards
Data on tobacco and alcohol consumption were collected in accordance with World Health Organization standards and alcohol risk data were reported in accordance with the current 2009 National Health and Medical Research Council’s ‘Australian Guidelines to Reduce Health Risks from Drinking Alcohol’.

Australian and New Zealand Standard Classification of Occupations (ANZSCO) and Australian and New Zealand Standard Industry Classification (ANZSIC) codes were used as the code-frame for questions relating to occupation and industry. 

Type of estimates available
Unadjusted estimates of drug use prevalence, attitudes and beliefs are most commonly reported. In addition, some population estimates and age-standardised data are available for some aspects of the collection. Time series data are also presented for most estimates in the 2013 NDSHS report.

Accuracy:Help on this term

Perceptions of behaviour
It is known from past studies of alcohol and tobacco consumption that respondents tend to underestimate actual consumption levels (Stockwell et al. 2004). There are no equivalent data on the tendencies for under- or over-reporting of actual illicit drug use.

However, illicit drug users, by definition, have committed illegal acts. They are, in part, marginalised and difficult to reach. Accordingly, estimates of illicit drug use and related behaviours are likely to be underestimates of actual practice

Sample design
The sample was stratified by region (15 strata in total ─ capital city and rest of state for each state and territory, with the exception of the Australian Capital Territory, which operated as one stratum). To produce reliable estimates for the smaller states and territories, sample sizes were boosted in Tasmania, the Australian Capital Territory and the Northern Territory.

The over-sampling of lesser populated states and territories produced a sample that was not proportional to the state/territory distribution of the Australian population aged 12 years or older. Weighting was applied to adjust for imbalances arising from execution of the sampling and differential response rates, and to ensure that the results relate to the Australian population.

Sampling error
The measure used to indicate reliability of individual estimates reported in 2013 was the relative standard error (RSE). Only estimates with RSEs of less than 25% are considered sufficiently reliable for most purposes. Results subject to RSEs of between 25% and 50% should be considered with caution and those with relative standard errors greater than 50% should be considered as unreliable for most practical purposes.


Non-sampling error
In addition to sampling errors, the estimates are subject to non-sampling errors. These can arise from errors in reporting of responses (for example, failure of respondents’ memories, incorrect completion of the survey form), the unwillingness of respondents to reveal their true responses and the higher levels of non-response from certain subgroups of the population.

Reported findings are based on self-reported data and not empirically verified by blood tests or other screening measures.


Response rates and contact rates
Overall, contact was made with 48,579 in-scope households, of which 23,855 questionnaires were categorised as being complete and useable, representing a response rate for the 2010 survey of 49.1%, slightly lower than the drop and collect component of the 2010 survey (50.6%).
Some survey respondents did not answer all questions, either because they were unable or unwilling to provide a response. The survey responses for these people were retained in the sample, and the missing values were recorded as not answered. No attempt was made to deduce or impute these missing values.

A low response rate does not necessarily mean that the results are biased. As long as the non-respondents are not systematically different in terms of how they would have answered the questions, there is no bias. Given the nature of the topics in this survey, some non-response bias is expected. If non-response bias in the NDSHS is to be eliminated as far as possible, there would need to be additional work conducted to investigate the demographic profile of the non-respondents and the answers they may have given had they chosen to respond.

Indigenous Data
The survey was not specifically designed to obtain reliable national estimates for Aboriginal and Torres Strait Islander people, as there was no target sample size for Indigenous Australians. In the 2013 NDSHS, 1.9% of the sample (or approximately 461 respondents) identified as being of Aboriginal or Torres Strait Islander origin. The sample size for Indigenous Australians was smaller than anticipated based on population estimates, and so estimates based on this population group should be interpreted with caution.

The total population of Aboriginal and Torres Strait Islander people forms a very small part of the total Australian population. At the August 2011 census, the Aboriginal and Torres Strait Islander population was officially calculated at 670,000 people, or 2.1% of the total Australian population (ABS 2008b). At that time, about one-third (35%) of the Aboriginal and Torres Strait Islander population lived in Major cities, 22% in Inner regional areas, 22% in Outer regional areas, 8% in Remote areas and 14% in Very remote areas (ABS 2013).


The Aboriginal and Torres Strait Islander population living in Very remote areas shows other differences to populations living in Major cities including in household structure, size and age distribution. The NDSHS sample design is stratified by region and not by remoteness. Due to this sampling design, the NDSHS sample of Indigenous Australians living in Very remote areas comprised of 9% of the population in those regions compared with 14% of Indigenous Australians living in Very remote areas based on the 2011 Census (ABS 2012). Therefore, Aboriginal and Torres Strait Islander people in Very remote areas are under represented, and it becomes difficult to generalise results from Major cities and regional areas to the whole Indigenous population.


The sampling method employed for the NDSHS invited one participant aged over 12 years to take part in the survey. The sample strategy did not take into account the size of the household selected. This is an issue for respondent selection for Indigenous Australians, as often they live in larger households compared with non-Indigenous Australians. This selection process means that Aboriginal and Torres Strait Islander people are proportionately less likely to be selected.


The NDSHS uses a self-completion questionnaire, and requires good comprehension of the English language (as it is not translated into other languages) and the ability to follow instructions. Practicality of the survey design meant that some Aboriginal communities and those with low levels of English literacy may have been excluded.

Coherence:Help on this term

Surveys in this series commenced in 1985. Over time, modifications have been made to the survey’s methodology and questionnaire design. The 2013 survey differs from previous versions of the survey in some of the questions asked and also used three follow up attempts by interviewers instead of the two used in 2010. 

Methodology
The 2013 survey was the second to exclusively use the drop and collect method, the first being 2010. In 2007 and 2004, a combination of computer-assisted telephone interviews (CATI) and drop and collect methods were used, and in earlier waves, personal interviews were also conducted.

The change in methodology in 2010 does have some impact on time series data, and users should exercise some degree of caution when comparing data over time.

Fieldwork was conducted between July and December 2013, slightly later than in previous wave. The collection period also coincided with the 2013 federal election, although no questionnaires were placed on that day.

Sample
To produce reliable estimates for the smaller states and territories, sample sizes were boosted in Tasmania, the Australian Capital Territory and the Northern Territory.

In 2013 and 2010, to improve the geographic coverage of the survey, interviewers were flown to Very remote areas selected in the sample. In previous surveys, some Very remote areas that were initially selected in the sample would have been deemed inaccessible and not included in the final sample.

Questionnaire
The 2013 questionnaire was modelled on the 2010 version, to maintain maximum comparability. However, some refinements were made to ensure the questions remained relevant and useful. For more information on questionnaire changes in 2013 see Chapter 1 of the 2013 NDSHS report.

Comparison with other collections
Comparisons of data from previous waves of the NDSHS, the Australian Health Survey and the Australian School Student’s Alcohol and other Drug Survey show variations in estimates. Differences in scope, collection methodology and design may account for this variation and comparisons between collections should be made with caution. 

There is more than one data source for information about tobacco, alcohol and other drug use among Aboriginal and Torres Strait Islander people. The most common data sources used for reporting the use of tobacco, alcohol and other drugs by Indigenous Australians are the National Aboriginal and Torres Strait Islander Social Survey (NATSISS) and the Australian Aboriginal and Torres Strait Islander Health Survey (AATSIHS).
Differences between the surveys vary considerably and include the extent to which remote areas were surveyed, the age groups included and the sample sizes. The questions asked in the surveys also differ considerably. So the results from the surveys are not directly comparable. It is important to keep this in mind when considering data from each of the surveys—results that may initially seem to contradict one another may be simply applicable to different groups within the population.
The 2012–13 AATSIHS estimated that around 41% of Indigenous Australians aged 15 years or older were daily smokers (ABS 2013), while the 2013 NDSHS estimated that figure to be about 32%.

Comparisons between Indigenous and non-Indigenous Australians can be made using data from the AATSIHS results and the 2011–12 National Healthy Survey. The surveys showed that after adjusting for differences in age structure between the two populations, Aboriginal and Torres Strait Islander people aged 15 years and over were 2.6 times as likely as non-Indigenous people to be current daily smokers (39.8% compared with 15.4%, respectively). In comparison, results from the 2013 NDSHS showed that Indigenous Australians aged 14 years or older were 2.5 times as likely as non-Indigenous Australians to smoke daily (31.6% compared with 12.4%). So while the estimated proportion of smokers from the NDSHS is lower than the AATSIHS and National Health Survey estimates, the relative proportions are very similar.

Analysis
The alcohol risk calculation (lifetime risk and single occasion risk) was revised in 2013. In previous years (2010 and earlier) a very small proportion of recent drinkers who did not provide information on quantity of alcohol consumed were assumed to be ‘low risk’. In 2013, these drinkers were excluded from alcohol risk analysis and trend data was revised (2001 to 2010) and will not match data presented in previous reports. The denominators used to calculate a person’s drinking status and their alcohol risk levels are slightly different and therefore the proportion of ‘abstainers’ no longer equates to the proportion of those who ‘never drank’ and ‘ex-drinkers’ combined.

Data products

Implementation start date:Help on this term01/12/2013

Source and reference attributes

Submitting organisation:Help on this termTobacco, Alcohol and Other Drug Unit, Australian Institute of Health and Welfare.
Steward:Help on this termAustralian Institute of Health and Welfare

Relational attributes

Related metadata references:Help on this term

Supersedes National Drug Strategy Household Survey 2010 – Data Quality Statement AIHW Data Quality Statements, Archived 25/11/2014

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